Unlike the model CLIMBER-2 (which has a complex relationship between the input
and the output and also a large computational cost) our conceptual model can
be used for a detailed investigation of the SR, e.g. because the
dynamics of the model is simple and precisely known and because probability
measures (such as waiting time distributions) can be explicitly computed. In fact, the
resonant pattern in the conceptual model (Fig. REF ) is due to
two time-scale matching conditions: The noise level is such that the average
waiting time between successive noise-induced transitions is comparable to
half of the period of the periodic forcing, and also comparable to the
relaxation times \(\tau _{0}\)  and \(\tau _{1}\)  of the threshold function (compare
Fig. REF b). This situation is different from
the usual SR, in which thresholds (or potentials) are constant in time (apart
from the influence of the periodic input). In the
usual SR, only one time-scale matching condition exists
[1]}, namely the one that the average waiting time between
successive noise-induced transitions (i.e. the inverse of the so-called
Kramers rate) is comparable to half of the period of the periodic forcing.
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